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      06-27-2019, 08:30 PM   #4

Drives: '17 328d Wagon, '21 M2 Comp
Join Date: Sep 2016
Location: Bay Area, CA

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Originally Posted by CanAutM3 View Post
If you know the front are progressive, what do you expect as an answer regarding their rates?
They look like dual rate springs to me (hence the plastic covering on the coils that will bind first). BMW specs the initial and final spring rates (but unfortunately I don't have them) based upon the docs I saw for the F8x ZCP and M2 rear springs (they also have the coverings for coil bind in the initial rate coils). For the F8x ZCP and M2 springs BMW has a force graph showing force per distance compressed with a very distinct knee/bend in it when the rate shifts from the initial one to the final one (not a continuously variable spring rate).

Bilstein gives you the final spring rate on the progressive springs in their coil overs.